Conventionally, a power converter including an inverter circuit has been known. The inverter circuit is configured to convert, by switching control, a direct current power to an alternating current power having a variable frequency and a variable voltage with high efficiency.
Examples of the power converter of this type include a so-called “electrolytic capacitor-less inverter circuit” using a low-capacity smoothing capacitor for a direct current link (see, e.g., Patent Document 1). In the electrolytic capacitor-less inverter circuit, e.g., a smoothing capacitor having a low capacity of about several hundred microfarads is provided on an output side of a diode rectifier circuit, instead of providing a conventional high-capacity smoothing capacitor (electrolytic capacitor). In the electrolytic capacitor-less inverter circuit to which a three-phase full-wave rectified alternating current is input, failure of a motor, such as vibration and noise, occurs in a control state (hereinafter referred to as an “over-modulation state”) in which a direct current link voltage pulsates with a frequency six times the frequency of a power supply (i.e., the frequency of a three-phase alternating current) and a fundamental voltage vector does not include a zero vector (i.e., a voltage vector for which a motor terminal voltage is zero). Typically, over-modulation control is not performed in a three-phase electrolytic capacitor-less inverter, resulting in a decrease in rate of voltage utilization and an increase in device loss in the three-phase electrolytic capacitor-less inverter.